- Turn off Wi-Fi Assist on your iPhone under Settings > Mobile Service.
- Disable Limit IP Address Tracking for Wi-Fi from Settings > Wi-Fi.
Basic Fixes
- Move close to your router : Poor Wi-Fi signal can force your iPhone to switch to mobile data instead of Wi-Fi.
- Connect to the 5GHz frequency band : Your iPhone will receive more Wi-Fi signal strength and faster speeds than the 2.4 GHz frequency band, preventing iOS from switching to mobile data.
- Forget and reconnect to the Wi-Fi network : Open the Settings app > select Wi-Fi > tap on i next to the connected network > select Forget This Network to remove it. Next, tap the Wi-Fi network and connect it using its passcode.
- Turn off mobile data manually : Open the Settings app > select Mobile Service > toggle off Mobile Data.
- Update iOS : Head to iPhone settings > select General > tap Software Update. Select Update Now (if available) to install new updates.
Fix 1: Disable Wi-Fi Assist
The Wi-Fi Assist feature on iOS automatically switches your iPhone to mobile data from Wi-Fi when it detects a poor Wi-Fi network connection. Disable it to prevent the switch.
Open the Settings app > select Mobile Service > scroll to the bottom and disable Wi-Fi Assist .

Fix 2: Turn off Low Data Mode for Wi-Fi
An active Low Data Mode on your Wi-Fi network can interrupt the internet connectivity, compelling your iPhone to switch to mobile data. Disable it manually under Wi-Fi settings.
Select Wi-Fi under iPhone settings > tap on i next to the connected network > toggle off the Low Data Mode .

Fix 3: Disable Limit IP Address Tracking for Wi-Fi
The Limit IP Address tracking hides your IP address from known trackers in Safari and Mail over Wi-Fi. If Apple servers are down or Wi-Fi is slow, iOS may automatically switch to mobile data from Wi-Fi. Disable the feature to avoid the scenario.
Open Wi-Fi settings on your iPhone ( Settings > Wi-Fi ) > tap on i next to the connected network > toggle off Limit IP Address Tracking .

Fix 4: Reset Network Settings
Lastly, reset network settings on your iPhone to remove incorrect network configurations forcing iOS to switch to mobile data from Wi-Fi.
Step 1: Select General under iPhone Settings > tap on Transfer or Reset iPhone .

Step 2: Tap on Reset > select Reset Network Settings . When prompted, type your device passcode to confirm the action.
